The present invention relates to a mechanical locking mechanism and an injector head employing the mechanism, and more specifically, it relates to an improvement of a structure for attaining miniaturization of a mechanical locking mechanism and an injector head employing the mechanism.
In recent years, various ones are developed as apparatuses testing functions of a human body. There is a circulatory organ X-ray diagnostic apparatus for diagnosing the functions of circulatory organs of a human body as one of these apparatuses. In this circulatory organ X-ray diagnostic apparatus, an injector head for injecting a contrast medium into a patient is employed.
According to the structure of a general injector head, a safety device for mechanically limiting movement of a plunger for moving a piston in a syringe filled with a contrast medium is provided. When providing this safety device on the injector head, the injector head tends to be large-sized.
In an injector head disclosed in Japanese Patent Laying-Open No. 10-244002, on the other hand, a structure attaining miniaturization of the injector head by providing a mechanical stopper arranged coaxially with a plunger for sliding in the axial direction of the plunger is employed.
According to the structure of the aforementioned conventional injector head, however, the structure of mechanically stopping the plunger having the largest torque itself with the mechanical stopper is employed. When mechanically stopping the plunger with the mechanical stopper, therefore, stress applied to the plunger, the mechanical stopper and other components increases.
Consequently, it forms the design basis to withstand this stress in strength design of the components such as the plunger subjected to application of the stress, and size increase of these components cannot be avoided. Consequently, there is a limit in the point of attaining miniaturization of the injector head.
Accordingly, an object of the present invention is to attain further miniaturization and simplification of a mechanical locking mechanism and an injector head employing the mechanism while keeping a mechanical safety mechanism of the mechanical locking mechanism and the injector head employing the mechanism.
In a mechanical locking mechanism based on the present invention, it is a mechanical locking mechanism for stopping a movable shaft capable of reciprocation, and comprises a movable shaft drive for converting rotary motion of a drive to motion of a prescribed direction in order to supply reciprocation to the aforementioned movable shaft and a safety device for restraining rotation of a rotary shaft of the aforementioned drive by a mechanical operation when the aforementioned movable shaft moves beyond a predetermined position.
Thus, torque caused on the rotary shaft of the drive is by far smaller than torque caused on the movable shaft, and hence it is possible to stop movement of the movable shaft with small force by restraining rotation of the rotary shaft of the drive by a mechanical operation. Therefore, stress applied to components forming the safety device also reduces and it is possible to attain miniaturization of these components and miniaturization of the mechanical locking mechanism following the same.
In order to execute the aforementioned invention in a preferable state, the following structure is employed: The aforementioned safety device includes a locking device provided in the vicinity of the aforementioned rotary shaft to be capable of restraining rotation of the rotary shaft of the aforementioned drive and a trigger device mechanically operating the aforementioned locking device so that the aforementioned locking device restrains the aforementioned rotary shaft when the aforementioned movable shaft moves beyond the predetermined position.
Further, the aforementioned locking device is provided to be capable of selecting a first position restraining rotation of the aforementioned rotary shaft and a second position liberating rotation of the said rotary shaft, and the aforementioned trigger device includes a detection mechanism for mechanically detecting a moving end of the aforementioned movable shaft and a link mechanism setting the aforementioned locking device on the first position by the aforementioned detection mechanism when the aforementioned movable shaft moves beyond the predetermined position.
This structure makes detection of the position of the movable shaft implementable by the detection mechanism consisting of only a mechanical structure, whereby safety of the operation of the mechanical locking mechanism can be attained regardless of a failure of electric control.
In an injector head based on the present invention, it is an injector head provided therein with a syringe filled with a contrast medium, and comprises a plunger capable of reciprocating in a direction of movement of a piston in the aforementioned syringe, a plunger drive for converting rotary motion of a motor to linear motion in order to supply reciprocation to the aforementioned plunger and a safety device for restraining rotation of a rotary shaft of the aforementioned motor by a mechanical operation when the aforementioned plunger moves beyond a predetermined position.
Thus, torque caused on the rotary shaft of the motor is by far smaller than torque caused on the plunger, and hence it is possible to stop movement of the plunger with small force by restraining rotation of the rotary shaft of the motor by a mechanical operation. Therefore, stress applied to components forming the safety device also reduces and it is possible to attain miniaturization of these components and miniaturization of the injector head following the same.
In order to execute the aforementioned invention in a preferable state, the following structure is employed: The aforementioned safety device includes a locking device provided in the vicinity of the aforementioned rotary shaft to be capable of restraining rotation of the rotary shaft of the aforementioned motor and a trigger device mechanically operating the aforementioned locking device so that the aforementioned locking device restrains the aforementioned rotary shaft when the aforementioned plunger moves beyond the predetermined position.
Preferably, the aforementioned locking means is provided to be capable of selecting a first position restraining rotation of the aforementioned rotary shaft and a second position liberating rotation of the aforementioned rotary shaft, and the aforementioned trigger device includes a detection mechanism for mechanically detecting a moving end of the aforementioned plunger, and a link mechanism setting the aforementioned locking device on the first position by the aforementioned detection mechanism when the aforementioned plunger moves beyond the predetermined position.
This structure makes detection of the position of the plunger implementable by the detection mechanism consisting of only a mechanical structure, whereby safety of the operation of the injector head can be attained regardless of a failure of electric control.
As a further preferable mode in the aforementioned mechanical locking mechanism and injector head, the aforementioned locking device includes a fixed lock ring provided around the aforementioned rotary shaft and including a groove portion having such a sliding surface that the distance between the sliding surface and the center of the aforementioned rotary shaft gradually shortens along a prescribed rotational direction of the aforementioned rotary shaft on a side facing the aforementioned rotary shaft, a lock pin arranged in the aforementioned groove portion and a movable lock ring holding the aforementioned lock pin to be movable between a first position locating the aforementioned lock pin between a surface of the aforementioned sliding surface most shortening the distance between the sliding surface and the aforementioned rotary shaft and the aforementioned rotary shaft and restraining rotation of the aforementioned rotary shaft by a wedge effect and a second position liberating rotation of the aforementioned rotary shaft in the aforementioned groove portion.
Further, the aforementioned detection mechanism includes a follower rotary shaft rotating following rotation of the aforementioned drive or the aforementioned motor, a body plate having the same rotation center as the rotation center of the aforementioned follower rotary shaft, a first gear having the same rotation center as the rotation center of the aforementioned follower rotary shaft, to which rotation of the aforementioned follower rotary shaft is transmitted through a first gear mechanism supported on the peripheral portion of the aforementioned body plate and a second gear having the same rotation center as the rotation center of the aforementioned follower rotary shaft, having a specific rotation control mechanism and arranged to be opposite to the aforementioned first gear, a surface of either one of the aforementioned first gear and the aforementioned second gear opposed to the other gear is provided with a pin projecting toward the other gear, a surface of the other gear opposed to one of the gears is provided with a ring-shaped guide slit having both end portions and extending along the rotation locus of the pin to be capable of receiving the aforementioned pin, and the aforementioned link mechanism has an engaging pin provided on the aforementioned movable lock ring, an operating mechanism provided to be rotatable about a prescribed axis for rotating the aforementioned movable lock ring so that the aforementioned lock pin is on the first position with an end engaging with aforementioned engaging pin and a link bar having an end coupled to the peripheral portion of the aforementioned body plate by a universal joint and another end coupled to the other end of the aforementioned operating mechanism by a universal joint.
Further, the aforementioned operating mechanism has an electric signal generator converting movement of the aforementioned operating mechanism to an electric signal.
In addition, the aforementioned trigger device has a device limiting the stroke of the aforementioned movable shaft or the aforementioned plunger.